Jim Mullin

Video data and video links in mediated communication: what do users value?

Abstract Most studies of video-mediated, computer-supported cooperative work have investigated the impact of video conference communication links between users. Fewer studies have explored the use of multimedia systems which provide video data. In our study, the perceived benefits of these two sorts of video provision have been directly compared. We explored how users rate the value and usefulness of video links and video data in the same collaborative task, where the video links and data were delivered at different frame rates. Our comparisons of the perceived relative values of teledata and telepresence are based on the responses of 117 users each of whom took part in a session lasting around 45 min in one of the two simulations. Both studies manipulated the quality of multimedia delivery for telepresence and teledata in the same way. The simulations were: (i) the Travel Service Simulation where participants plan a holiday itinerary and (ii) the Financial Service Simulation where participants choose a property and arrange an appropriate mortgage. Participants produced very similar ratings for the perceived quality of the telepresence and the teledata. Subjects across both studies were also in broad agreement on the relative usefulness of the various kinds of multimedia data, teledata being regarded as generally more useful than telepresence. Subjects in both studies tended to rank teledata high in terms of (a) what was most useful, (b) what was the most important feature to preserve and (c) what was the most important to improve. For these multimedia customer services, teledata is more highly valued by users than telepresence. Within such complex multimedia applications, the indication for service delivery then is that, if bandwidth is limited, it would be better assigned to teledata services than to telepresence.

Impact of video-mediated communication on simulated service encounters

The results are reported of three studies of collaborative problem-solving in a simulated travel agency where communication between travel agent and customers is supported by a videolink and shared multimedia tools. The video-mediated contexts (VMCs) were compared with face-to-face and audio-only interactions in terms of the success of the task outcome, the process of communication and decision making and user satisfaction. VMC did not deliver the same benefits as face-to-face interactions. The possible reasons for this are explored as well as the implications of the data for evaluation techniques.

Impact of video frame rate on communicative behaviour in two and four party groups

There has been relatively little research on the impact of different levels of video quality on users of multimedia communication systems. This paper describes a study examining the impact of two levels of video frame rate on pairs and groups of four engaged on a design task, looking at one particular aspect of communication, namely reference. It was found that a low frame rate made speakers more communicatively cautious, using longer descriptions and more elaborations to refer to pictures used in the task, possibly as a result of being less certain that they had been understood. This only occurred in the two party groups despite a prediction that groups of four would be affected most by the frame rate manipulation. This study shows that video quality can have subtle effects on communication and that identical levels of quality may have different effects depending on the situation.

Effects of Magnesium Treatment in a Model of Internal Capsule Lesion in Spontaneously Hypertensive Rats

Background and Purpose— The study aim was to assess the effects of magnesium sulfate (MgSO4) administration on white matter damage in vivo in spontaneously hypertensive rats. Methods— The left internal capsule was lesioned by a local injection of endothelin-1 (ET-1; 200 pmol) in adult spontaneously hypertensive rats. MgSO4 was administered (300 mg/kg SC) 30 minutes before injection of ET-1, plus 200 mg/kg every hour thereafter for 4 hours. Infarct size was measured by T2-weighted magnetic resonance imaging (day 2) and histology (day 11), and functional recovery was assessed on days 3 and 10 by the cylinder and walking-ladder tests. Results— ET-1 application induced a small, localized lesion within the internal capsule. Despite reducing blood pressure, MgSO4 did not significantly influence infarct volume (by magnetic resonance imaging: median, 2.1 mm3; interquartile range, 1.3 to 3.8, vs 1.6 mm3 and 1.2 to 2.1, for the vehicle-treated group; by histology: 0.3 mm3 and 0.2 to 0.9 vs 0.3 mm3 and 0.2 to 0.5, respectively). Significant forelimb and hindlimb motor deficits were evident in the vehicle-treated group as late as day 10. These impairments were significantly ameliorated by MgSO4 in both cylinder (left forelimb use, P<0.01 and both-forelimb use, P<0.03 vs vehicle) and walking-ladder (right hindlimb score, P<0.02 vs vehicle) tests. Conclusions— ET-1–induced internal capsule ischemia in spontaneously hypertensive rats represents a good model of lacunar infarct with small lesion size, minimal adverse effects, and a measurable motor deficit. Despite inducing mild hypotension, MgSO4 did not significantly influence infarct size but reduced motor deficits, supporting its potential utility for the treatment of lacunar infarct.

Noninvasive Self-Gated Magnetic Resonance Cardiac Imaging of Developing Chick Embryos In Ovo

The chick embryo is a well-known model for cardiovascular research, in which it is commonly used for the study of cardiac development, though not to date cardiac function. In other animal models, magnetic resonance imaging (MRI) has evolved into a major noninvasive tool to study healthy and diseased hearts, for instance in assessing left ventricular function (ejection fraction, myocardial mass, and wall thickness) and infarct size and in assessing anatomic abnormalities. The lack of MRI application to chick embryos is partly due to the difficulty of monitoring chick ECG and respiration signals, which are conventionally essential in acquiring images free of motion artifact, by prospectively triggering the MR scanner. In the present study, we remove these obstacles by employing a self-gated cine MRI protocol that incorporates a navigator-based retrospective gating technique. The navigator signal …

Audio channel constraints in video-mediated communication

This study investigated the effects of two types of audio channels upon the effectiveness of task-based interactions in a video-mediated context (VMC). Forty undergraduates completed a collaborative task (The Map Task) using either a full or half-duplex audio channel. Their performance was compared to face-to-face interactions, taken from the Human Communication Research Centre corpus of Map Task Dialogues. Effects of varying the audio channel were explored by comparing task performance, patterns of speech, and establishment of mutual understanding. Users of the full-duplex VMC made insufficient allowance for the VMC context; they completed the task less accurately than face-to-face participants, and interrupted each other more frequently than other participants. Participants in the half-duplex VMC however performed as well as face-to-face participants. They made sensible adaptations to the constraints imposed by the half-duplex VMC context, producing longer dialogues, with more explicit turn-taking management, and taking greater care in establishing mutual knowledge.

In ovo non-invasive quantification of the myocardial function and mass of chick embryos using magnetic resonance imaging

Magnetic resonance imaging (MRI) has evolved as one of the major non‐invasive tools to study healthy and diseased hearts in animal models, especially rodent models. Even though, the chick embryo has long been used as a model for cardiovascular research, MRI has not yet been used for in vivo cardiac studies. Part of the reason for this is the difficulty in monitoring the ECG and respiration of the chick embryo in the magnet for gating purposes. To overcome this complication, this paper presents the use of retrospective Cine MRI to measure the cardiac function of chick embryos in ovo for the first time, without the need for respiratory or cardiac gating. The resulting left ventricular functional parameters, from six chick embryos at 20 days of incubation, were (mean ± SD) EDV 69 ± 15 µL, ESV 31 ± 7 µL, SV 38 ± 9 µL and EF 54.5 ± 2%. The use of retrospective Cine MRI at earlier stages of development is also discussed and difficulties have been highlighted. Copyright

Eye-Tracking Explorations in Multimedia Communications

Two studies are reported exploring the usefulness of eye-tracking techniques in illuminatingcomputer users’ behaviour in conducting collaborative tasks while supported by multimedia communications. We describe how the technology was deployed and the data we derived to explore the use of visual cues incomputer-supported collaborative problem solving. Participants made modest use of the video-link to their remote collaborator, devoting most of their visual attention to other onscreen resources. Varying the quality of this video-link did not influence its use. Eye-tracking was found to be a viable and useful evaluation technique in CSCW.

Sodium-23 magnetic resonance imaging has potential for improving penumbra detection but not for estimating stroke onset time

Tissue sodium concentration increases in irreversibly damaged (core) tissue following ischemic stroke and can potentially help to differentiate the core from the adjacent hypoperfused but viable penumbra. To test this, multinuclear hydrogen-1/sodium-23 magnetic resonance imaging (MRI) was used to measure the changing sodium signal and hydrogen-apparent diffusion coefficient (ADC) in the ischemic core and penumbra after rat middle cerebral artery occlusion (MCAO). Penumbra and core were defined from perfusion imaging and histologically defined irreversibly damaged tissue. The sodium signal in the core increased linearly with time, whereas the ADC rapidly decreased by >30% within 20 minutes of stroke onset, with very little change thereafter (0.5–6 hours after MCAO). Previous reports suggest that the time point at which tissue sodium signal starts to rise above normal (onset of elevated tissue sodium, OETS) represents stroke onset time (SOT). However, extrapolating core data back in time resulted in a delay of 72±24 minutes in OETS compared with actual SOT. At the OETS in the core, penumbra sodium signal was significantly decreased (88±6%, P=0.0008), whereas penumbra ADC was not significantly different (92±18%, P=0.2) from contralateral tissue. In conclusion, reduced sodium-MRI signal may serve as a viability marker for penumbra detection and can complement hydrogen ADC and perfusion MRI in the time-independent assessment of tissue fate in acute stroke patients.

Serial postmortem relaxometry in the normal rat brain and following stroke

To investigate MRI for noninvasive autopsy by means of measurements of serial changes in relaxation parameters of the rat brain during the postmortem interval.